Such steering rods are adjustable in height, in their position relative to the steerer, in general via a two-part telescopic steering column which is then fixed at the desired height. The steering rod itself is hinged to the steering column by means of an articulated arm and is fixed to said column by means of a tube clamp. If the tube clamp is opened, or slackened, the steering rod itself can be rotated and hence the gripping position relative to the steerer can be changed. The two adjustment facilities, both the height adjustment and the rotation, are generally only used once, i.e. for adaptation to the person steering, since fixing must be very reliable and must on no account be loosened during the journey.
Particularly when riding for sport, as, for example, when riding mountain bikes, however, this fixing of the steering rod is found to be extremely disadvantageous. Thus, the steering rod is generally felt to be too low or too far away from the body when ascending but too high or too close to the body when descending. After long riding times, it is desired to adjust--generally raise--the steering rod in order to be able to assume a relaxed posture.
Various proposals have been made for adjusting steering rods in terms of height and/or position relative to the rider.
Thus, U.S. Pat. No. 2,594,451 describes an adjusting facility in which a spring-loaded pin locks in depressions in a disk coordinated with the steering column. However, this connection will prove insufficient when the wheel is subjected to a relatively strong load, even when the articulated arm bearing the articulated rod is additionally clamped to the disk. Even additional securing by means of a crosspin prevents only unintentional removal of the pin from the depression. The adjustment itself requires three fastening steps; fixing the position by means of one--essentially weak--pin alone appears insecure and susceptible to breakage.
In the adjusting apparatus described in French Patent 404,027, an articulated part connected to the steering column is gripped by the jaws of a support arm holding the steering column, both the articulated part and the jaws having flutings converging in a ray-like manner. When the support arm is rotated, the diametrally opposed locking surfaces on the jaws of the support arm and on the articulated part can lock with one another because the jaws as such are resilient. The desired rotation position is then secured by means of a screw bolt. Owing to frequently made adjustments and/or extensive use of the bicycle, fastening means will have a certain play and, after a certain time, this connection will become insecure, precisely because of the resilience of the jaws. There is the danger that--particularly during cross-country journeys, impacts will slacken the connection and the support arm with the steering rod will bend in an uncontrollable manner.